Method of manufacturing semiconductor device having tie bars for interconnecting leads

Abstract

A semiconductor element is first fixed on a frame. The semiconductor element and a plurality of leads are connected together. The semiconductor element is sealed with molding resin, to thereby fabricate a package having a length per side of 14 mm or more. After tie bars interconnecting a plurality of leads have been cut, a package is subjected to heat treatment at a predetermined temperature.

What is claimed is:  
     
       1. A method of manufacturing a semiconductor device comprising the steps of: 
       fixing a semiconductor element on a frame;  
       connecting the semiconductor element with a plurality of leads;  
       sealing the semiconductor element with molding resin, to thereby fabricate a package having a length per side of 14 mm or more;  
       cutting tie bars interconnecting the plurality of leads; and  
       subjecting the package to heat treatment at a predetermined temperature after cutting of the tie bars.  
     
     
       2. The method of manufacturing a semiconductor device according to  claim 1 , wherein the package is subjected to the heat treatment in a state in which internal stress of the package can be alleviated. 
     
     
       3. The method of manufacturing a semiconductor device according to  claim 1 , wherein the predetermined temperature is 175° C.±10° C. 
     
     
       4. The method of manufacturing a semiconductor device according to  claim 1 , further comprising a step of plating the surfaces of the leads after cutting of the tie bars and before the package is subjected to the heat treatment. 
     
     
       5. The method of manufacturing a semiconductor device according to  claim 1 , wherein pinch cutting sections connecting corners of the package with a framework are cut simultaneously with cutting of the tie bars, or before the package is subjected to heat treatment but after cutting of the tie bars. 
     
     
       6. The method of manufacturing a semiconductor device according to  claim 1 , wherein the tie bars are provided at positions spaced 0.2 mm to 0.3 mm away from a mold line of the package and in parallel with the mold line. 
     
     
       7. The method of manufacturing a semiconductor device according to  claim 1 , wherein the tie bars are provided at positions spaced 1.7 mm away from a framework and in parallel with a mold line of the package. 
     
     
       8. The method of manufacturing a semiconductor device according to  claim 1 , wherein the package is a TQFP or LQFP. 
     
     
       9. The method of manufacturing a semiconductor device according to  claim 1 , wherein the frame is formed from copper or iron as a principal constituent.